Instruments and Methods for Thermal Tissue Treatment

ABSTRACT

Disclosed herein are high efficiency surgical devices and methods of using same using radio frequency (RF) electrical power and/or electrically heated filaments to destroy tumors, form lesions, denaturize, desiccate, coagulate and ablate soft tissues, as well as to drill, cut, resect and vaporize soft tissues. According to the principles of this invention, the electrosurgical instruments can be used with externally supplied conductive or non-conductive liquids, as well as without externally supplied liquids, a mode of operation often referred to as “dry field” environment.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.12/033,987 filed Feb. 20, 2008, now U.S. Pat. No. 8,475,452 issued Jul.2, 2013, which, in turn, claims the benefit of U.S. ProvisionalApplication No. 60/902,548 filed Feb. 21, 2007. These prior applicationsare incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to the field of thermal tissuetreatment, and more particularly, to high efficiency surgicalinstruments and methods which use radio frequency (RF) electrical powerand/or electrically heated filaments to destroy tumors, form lesions,denaturize, desiccate, coagulate and ablate soft tissues, as well as todrill, cut, resect and vaporize soft tissues. According to theprinciples of this invention, the electrosurgical instruments of thepresent invention can be used to thermally treat target tissues ofinterest, either at the tissue surface, below the tissue surface or at asite remote therefrom, using externally supplied conductive ornon-conductive fluids, as well as without externally supplied liquids, amode of operation often referred to as “dry field” environment.

BACKGROUND OF THE INVENTION

Electrosurgical procedures are advantageous since they generally reducepatient bleeding and trauma. The devices used are electricallyenergized, typically using an RF generator operating at a frequency thatranges between 100 kHz to over 4 MHz. Due to their ability to providebeneficial outcomes with reduced patient pain and recuperation time,electrosurgical devices have recently gained significant popularityrecently. In common terminology and as used herein, the term “electrode”can refer to one or more components of an electrosurgical device (suchas an “active electrode” or a “return electrode”) or to the entiredevice, as in an “ablator electrode” or “cutting electrode”.Electrosurgical devices may also be referred to as electrosurgical“probes” or “instruments”.

Many types of electrosurgical instruments are currently in use, and canbe divided into two general categories: monopolar devices and bipolardevices. In the context of monopolar electrosurgical devices, the RFcurrent generally flows from an exposed active electrode, through thepatient's body, to a passive, return current electrode that isexternally attached to a suitable location on the patient body. In thismanner, the patient's body becomes part of the return current circuit.In the context of bipolar electrosurgical devices, both the active andthe return current electrodes are exposed, and are typically positionedin close proximity to each other, more frequently mounted on the sameinstrument. The RF current flows from the active electrode to the returnelectrode through the nearby tissue and conductive fluids.

The need to effectively yet minimally invasively treat tumor tissue froma patient's body arises in the context of many medical practice areas,including, but not limited to, oncology, ear nose and throat (ENT),urology, gynecology, laparoscopy and general surgery. More specifically,there is often a need to denaturize, desiccate or coagulate tissue anddestroy tumors in the liver, kidney, breast, lung, bone, lymph nodes,nerve ganglia and other organs. Such procedures are collectivelyreferred to as tissue ablation or lesion formation, and are often usedto destroy tumors without radical surgery. In such cases, an effectivetreatment is one in which the tumor itself, and perhaps a small marginof tissue around the tumor, is affected. The affected tumor tissue isnot immediately removed. Over time, the dead tissue will naturallyshrink, dissolve and, in some cases, be gradually replaced by scartissue.

Although the benefits of these procedures are well recognized by thoseof skill in the art, current electrosurgical instruments and proceduressuffer from very significant deficiencies. Quite often existinginstruments are composed of one or more needles which are electricallyenergized by radiofrequency. As a result, the energy deposition in thetissue is concentrated close to where the needle is positioned, leadingto overheating in the immediate region and under-heating in areasfarther away. The result is a highly non-homogeneous energy depositionand highly non-homogeneous lesion. It is inherently impossible toaccurately control the shape and size of the lesion formed with existinginstruments because the energy deposition and heating occurs from theinside out. However, in order to destroy a tumor, it is often necessary,yet undesirable, to also destroy a large margin of healthy tissue aroundthe tumor. As a result the current processes are inefficient, requirehigh power levels and therefore can lead to unnecessary complicationsand undesired side effects. In some cases, additional return electrodes(also called grounding pads or patient electrodes) are needed in orderto safely handle the high energy and high current required to performthe procedure. One such system marketed by Boston Scientific (Natick,Mass.) for lever ablation uses four patient electrodes simultaneously.

In view of these and other deficiencies, there is a need in the art forimproved electrosurgical instruments that are capable of creatinguniform lesions of a desired size and shape, capable of treating tissueand tumors from the outside in rather than from the inside out, andcapable of treating large and non uniform tumors and leaving healthytissue unharmed. There is also a need in the art for a high efficiencyelectrosurgical instrument capable of destroying the tumor at relativelylow power, thereby increasing patient safety and efficacy and reducingundesired side effects.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a highlyefficient, minimally invasive surgical instrument capable of overcomingthe deficiencies discussed above. More particularly, in view of theever-present need in the art for improvements in electrode design, it isan object of the present invention to provide a highly efficient andefficacious electrosurgical instrument suitable for the thermaltreatment of tumors, more particularly a radiofrequency electrosurgicaldevice adapted for enhanced lesion formation.

Electrosurgical instruments of the present invention may be designed tobe inserted directly, to penetrate the patient tissue at the desiredlocation, or alternatively to be introduced into the patient bodythrough a cannula, a resectoscope, an endoscope or an opening in thebody.

In certain embodiments, the electrosurgical instruments of the presentinvention may optionally be provided with means for externally supplyingirrigation liquid, either electrically conductive or non-conductive, tothe surgical site. In other embodiments, the electrosurgical instrumentof the present invention may be designed to function in the absence ofan external source of fluids, relying instead on the tissue propertiesor endogenous bodily fluids. As noted above, this mode of operation issometimes referred to as “dry field”.

In further embodiments, the electrosurgical instrument of the presentinvention may optionally be equipped with irrigation, aspiration orboth, as well as oscillatory or imitational motion.

The electrosurgical instrument of the present invention may be eithermonopolar or bipolar electrodes and may optionally be equipped with oneor more floating elements. “Floating” electrodes for electrosurgery aredescribed in co-pending U.S. patent application Ser. No. 10/911,309(published as US 2005-0065510) and Ser. No. 11/136,514 (published as US2005-023446), the contents of which are incorporated by reference hereinin their entirety.

In yet further embodiments, the electrosurgical instrument of thepresent invention may include an advanced active electrode designed tooperate at high temperatures for improved efficiency.

In yet further embodiments, the electrosurgical instrument of thepresent invention may be provided with one or more high-powered sourcesof non-coherent radiation to affect tissue surfaces.

In yet further embodiments, the electrosurgical instrument of thepresent invention may be designed to operate without contact between theelectrode and the tissue surface.

It will be understood by those skilled in the art that one or moreaspects of this invention can meet certain objectives, while one or moreother aspects can meet certain other objectives. Each objective may notapply equally, in all its respects, to every aspect of this invention.As such, the following objects should be viewed in the alternative withrespect to any one aspect of this invention:

Thus, it is an object of the present invention to provide anelectrosurgical instrument for thermal tissue treatment composed of:

-   -   (a) an elongate shaft having a proximal end configured for        connection to a power source and a distal end having an        electrode assembly mounted thereto;    -   (b) an electrode assembly comprising an active electrode, a        floating electrode, and an insulator separating the active and        floating electrodes and defining a cavity therebetween;    -   (c) a means for supplying an irrigant to the cavity;

wherein the insulator is formed from a nonconductive dielectric materialwhile said active and floating electrodes are formed from anelectrically conductive material;

wherein the active and floating electrodes are positioned in closeproximity to each other;

wherein the active electrode is connected via cabling disposed withinsaid shaft to said power source while the floating electrode is notconnected to a power source such that powering of the active electroderesults in flow of current from the active electrode to said floatingelectrode via the irrigant, thereby resulting in the heating of theirrigant and the generation of steam;

wherein the heated irrigant and steam contacts target tissue so as tothermally treat the target tissue of interest.

It is a further object of the present invention to provide anelectrosurgical instrument for sub-surface thermal treatment of targettissue composed of:

-   -   (a) an elongate shaft having a proximal end configured for        connection to a power source and a distal end having an        electrode assembly mounted thereto;    -   (b) an electrode assembly including (i) an insulating tubular        member, (ii) an active electrode disposed at the distal tip of        the insulating tubular member and connected via cabling disposed        within the shaft to said power source, and (iii) a tubular        conductive member concentrically disposed about the insulating        tubular member; and    -   (c) a switching means for alternately connecting and        disconnecting the conductive member to a power source;

wherein the insulating tubular member is formed from a nonconductivedielectric material while the active electrode and said conductivemember are formed from an electrically conductive material;

wherein the active and floating electrodes are positioned in closeproximity to each other but are prevented by the insulator from directlycontacting each other; and

wherein the active electrode takes the form of a tapered conical memberthat is sufficiently sharp to permit insertion of the electrode assemblyinto the target tissue.

It is yet a further object of the present invention to provide a methodfor thermally treating a target tissue in the body of a patientincluding the steps of:

-   -   (a) introducing an electrosurgical instrument the present        invention into the patient such that the electrode assembly is        in close contact with the target tissue;    -   (b) supplying an irrigant to the cavity defined between the        active and floating electrodes; and    -   (c) applying a high-frequency voltage to the active electrode;

wherein the high frequency voltage results not only in the flow ofcurrent among active electrode, floating electrode and target tissue butfurther results in the boiling of irrigant, such that expanding steamand heated irrigant flow from the cavity to the target tissue site,thereby thermally treating the target tissue.

The present invention relates generally to the field of thermal tissuetreatment, and more particularly, to high efficiency surgicalinstruments and methods which use radio frequency (RF) electrical powerand/or electrically heated filaments to destroy tumors, form lesions,denaturize, desiccate, coagulate and ablate soft tissues, as well as todrill, cut, resect and vaporize soft tissues. According to theprinciples of this invention, the surgical instruments of the presentinvention can be used with externally supplied conductive ornon-conductive liquids, as well as without externally supplied liquids,a mode of operation often referred to as “dry field” environment.

In one embodiment, the present invention provides a high efficiencyelectrosurgical instrument particularly suited to surface treatment oftissues, such a tumor tissues, the instrument including an active endhaving radiused corners and composed of a unique combination of activeelectrode, insulator, floating electrode and return electrode that limitsparking and tissue vaporization. Illustrative examples of this objectare set forth in FIGS. 1-22.

In another embodiment, the present invention provides a high efficiencyelectrosurgical instrument wherein the active electrode and floatingelectrode interact to boil an exogenous irrigant therebetween such thatlesion formation is accomplished primarily by steam and heated fluidwhich contact the tissue. Illustrative examples of this object are setforth in FIGS. 23-29.

In yet another embodiment, the present invention provides a highefficiency electrosurgical instrument particularly suited to sub-surfacetissue treatment, the instrument including a switching means that allowsa circumferential electrode to function as a floating electrode whendrilling into the tissue, and subsequently as an active electrode tothermally treat tissue when in close proximity to a target site.Illustrative examples of this object are set forth in FIGS. 30-32.

In a further embodiment, the present invention provides a highefficiency electrosurgical instrument particularly suited to sub-surfacetissue treatment, wherein the instrument uses heated irrigant and steamgenerated within the probe to thermally treat tissue in close proximity.In one embodiment, the heating occurs within the instrument tip, betweenan active tip electrode and a floating electrode in contact with thetissue. Illustrative examples of this object are set forth in FIGS.33-36.

In yet a further embodiment, the present invention provides a highefficiency electrosurgical instrument particularly suited to sub-surfacetissue treatment, the instrument including an active electrode isinserted into the tissue and a return electrode positioned on thesurface of the organ in close proximity to the active electrode so as tofocus the current flow in the desired region. Illustrative examples ofthis object are set forth in FIGS. 37-38.

In yet a further embodiment, the present invention provides a highefficiency electrosurgical instrument particularly suited to thermaltissue treatment, the instrument composed of a monopolar probe withlow-flow irrigation to prevent tissue charring. Illustrative examples ofthis object are set forth in FIGS. 39-41.

In yet a further embodiment, the present invention provides a highefficiency electrosurgical instrument particularly suited to thermaltissue treatment, wherein the instrument includes a heated filament togenerate plasma channels between the filament and the surface.Illustrative examples of this object are set forth in FIGS. 42-60.

In yet a further embodiment, the present invention provides a minimallyinvasive instrument particularly suited to thermal tissue treatment,wherein the instrument includes a heated filament emittingelectromagnetic radiation in the form of a non-coherent infra-red,ultraviolet and/or visible spectrum to achieve thermal surface treatmentand lesion formation. Illustrative examples of this object are set forthin FIGS. 61-62.

These and other objects and features of the invention will become morefully apparent when the following detailed description is read inconjunction with the accompanying figures and/or examples. However, itis to be understood that both the foregoing summary of the invention andthe following detailed description are of a preferred embodiment and notrestrictive of the invention or other alternate embodiments of theinvention. In particular, while the invention is described herein withreference to a number of specific embodiments, it will be appreciatedthat the description is illustrative of the invention and is notconstructed as limiting of the invention. Various modifications andapplications may occur to those who are skilled in the art, withoutdeparting from the spirit and the scope of the invention, as describedby the appended claims. Likewise, other objects, features, benefits andadvantages of the present invention will be apparent from this summaryand certain embodiments described below, and will be readily apparent tothose skilled in the art having knowledge of electrode design. Suchobjects, features, benefits and advantages will be apparent from theabove in conjunction with the accompanying examples, data, figures andall reasonable inferences to be drawn there-from, alone or withconsideration of the references incorporated herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and applications of the present invention will becomeapparent to the skilled artisan upon consideration of the briefdescription of the figures and the detailed description of the presentinvention and its preferred embodiments which follows:

FIG. 1 is a plan view of an insulator for a lesion formingelectrosurgical instrument formed in accordance with the principles ofthis invention.

FIG. 2 is a side elevational view of the objects of FIG. 1.

FIG. 3 is a bottom side plan view of the objects of FIG. 1.

FIG. 4 is a perspective view of the objects of FIG. 1.

FIG. 5 is an axial sectional view of the objects of FIG. 1 at locationA-A of FIG. 1.

FIG. 6 is a side elevational sectional view of the objects of FIG. 1 atlocation B-B of FIG. 1.

FIG. 7 is a plan view of an active electrode for a lesion formingelectrosurgical instrument formed in accordance with the principles ofthis invention.

FIG. 8 is a side elevational view of the objects of FIG. 7.

FIG. 9 is a perspective view of the objects of FIG. 7.

FIG. 10 is a distal axial view of the objects of FIG. 7.

FIG. 11 is a plan view of a floating electrode for a lesion formingelectrosurgical instrument formed in accordance with the principles ofthis invention.

FIG. 12 is a side elevational view of the objects of FIG. 11.

FIG. 13 is a bottom side plan view of the objects of FIG. 11.

FIG. 14 is a perspective view of the objects of FIG. 11.

FIG. 15 is an axial view of the objects of FIG. 11.

FIG. 16 is a plan view of a distal portion of a lesion formingelectrosurgical instrument formed in accordance with the principles ofthis invention.

FIG. 17 is a side elevational view of the objects of FIG. 16.

FIG. 18 is a bottom side plan view of the objects of FIG. 16.

FIG. 19 is a perspective view of the objects of FIG. 16.

FIG. 20 is an axial sectional view of the objects of FIG. 16 at locationC-C of FIG. 17.

FIG. 21 is a side elevational sectional view of the objects of FIG. 16at location D-D of FIG. 16.

FIG. 22 is an axial sectional view of the objects of FIG. 16 during useshowing current flow.

FIG. 23 is a plan view of a distal portion of an alternate embodimentelectrosurgical instrument adapted for thermal tissue treatment near atissue surface.

FIG. 24 is a side elevational view of the objects of FIG. 23.

FIG. 25 is a bottom side plan view of the objects of FIG. 23.

FIG. 26 is a side elevational sectional view of the objects of FIG. 23at location B-B of FIG. 23.

FIG. 27 is an axial sectional view of the objects of FIG. 23 at locationE-E of FIG. 24.

FIG. 28 is an axial sectional view of the objects of FIG. 23 in use in adry field environment.

FIG. 29 is an axial sectional view of the objects of FIG. 23 in use in aconductive fluid environment.

FIG. 30 is a perspective view of a distal portion of an alternateembodiment RF electrosurgical instrument adapted for thermal tissuetreatment at a location remote from the tissue surface (e.g.,sub-surface).

FIG. 31 is a plan view of the objects of FIG. 30.

FIG. 32 is a side elevational sectional view of the objects of FIG. 30at location A-A of FIG. 31.

FIG. 33 is a perspective view of a distal portion of an alternateembodiment RF electrosurgical instrument adapted for thermal tissuetreatment at a location remote from the tissue surface (e.g.,sub-surface).

FIG. 34 is a plan view of the objects of FIG. 33.

FIG. 35 is a side elevational sectional view of the objects of FIG. 34at location A-A of FIG. 34.

FIG. 36 is a sectional view of the objects of FIG. 33 during use.

FIG. 37 is a side elevational view of the distal portion of an alternateembodiment.

FIG. 38 is a side elevational view of the distal portion of an alternateembodiment.

FIG. 39 is a perspective view of the distal portion of an alternateembodiment.

FIG. 40 is a plan view of the objects of FIG. 38.

FIG. 41 is a side elevational sectional view of the objects of FIG. 38at location A-A of FIG. 39 during use.

FIG. 42 is a perspective view of an alternate embodiment probe.

FIG. 43 is a plan view of the objects of FIG. 42.

FIG. 44 is a side elevational view of the objects of FIG. 42.

FIG. 45 is an expanded view of the distal portion of the instrument ofFIG. 42.

FIG. 46 is a side elevational sectional view of the objects of FIG. 44at location A-A of FIG. 45.

FIG. 47 is a side elevational sectional view of the objects of FIG. 44at location B-B of FIG. 45.

FIG. 48 is an axial sectional view of the objects of FIG. 44 at locationC-C of FIG. 45.

FIG. 49 is a perspective view of the objects of FIG. 45.

FIG. 50 is a side elevational sectional view of the distal portion ofthe instrument of FIGS. 42 in use.

FIGS. 51(A) and (B) is a schematic representation of the probe of FIG.42 in use.

FIG. 52(A) is a schematic representation of the distal end portion ofthe instrument of FIG. 42. FIG. 52(B) is an axial sectional view of theobjects of FIG. 51(A) at location A-A of FIG. 51(A). FIG. 52(C) is anaxial sectional view of an alternate embodiment at location A-A of FIG.51(A).

FIG. 53 is a schematic representation of a distal portion of analternate embodiment having a coil filament.

FIG. 54 is a schematic representation of a distal portion of analternate embodiment having a filament integral with the conductivemembers.

FIG. 55 is a schematic representation of a distal portion of analternate embodiment which uses micro-sparking between the conductivemembers rather than a filament.

FIG. 56 is a schematic representation of a distal portion of analternate embodiment which uses a UV lamp as a heat source.

FIG. 57 is a schematic representation of a distal portion of analternate embodiment which has no filament for micro-sparking.

FIG. 58 is a schematic representation of a distal portion of analternate embodiment which uses dielectric breakdown to producemicro-sparking.

FIG. 59 is a schematic representation of a distal portion of analternate embodiment which does not use an external power source formicro-sparking or heating a filament.

FIG. 60(A) is a schematic representation of a distal portion of analternate embodiment which is configured for gas flow outward from theinstrument tip. FIG. 60(B) is a schematic representation of a distalportion of an alternate embodiment which is configured for gas flowinward from the instrument tip.

FIG. 61 is a schematic representation of an alternate embodiment fortreating a cavity in a body using a miniature electromagnetic energysource.

FIG. 62 is a schematic representation of an alternate embodiment fortreating a surface using a miniature electromagnetic energy source.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This present invention constitutes a marked improvement in the field ofelectrosurgery, more particularly, to high efficiency electrosurgicalsurgical instruments and methods which use radio frequency (RF)electrical power and/or electrically heated filaments to destroy tumors,form lesions, denaturize, desiccate, coagulate and ablate soft tissues,as well as to drill, cut, resect and vaporize soft tissues.

Although any methods and materials similar or equivalent to thosedescribed herein can be used in the practice or testing of embodimentsof the present invention, the preferred methods, devices, and materialsare now described. However, before the present materials and methods aredescribed, it is to be understood that this invention is not limited tothe particular compositions, methodologies or protocols hereindescribed, as these may vary in accordance with routine experimentationand optimization. It is also to be understood that the terminology usedin the description is for the purpose of describing the particularversions or embodiments only, and is not intended to limit the scope ofthe present invention which will be limited only by the appended claims.

Elements of the Present Invention

In the context of the present invention, the following definitionsapply:

The words “a”, “an”, and “the” as used herein mean “at least one” unlessotherwise specifically indicated.

In common terminology and as used herein, the term “electrode” may referto one or more components of an electrosurgical device (such as anactive electrode or a return electrode) or to the entire device, as inan “ablator electrode” or “cutting electrode”. Such electrosurgicaldevices are often interchangeably referred to herein as electrosurgical“probes” or “instruments”.

The present invention makes reference to an “active electrode” or“active element”. As used herein, the term “active electrode” refers toone or more conductive elements formed from any suitable metallicmaterial, such as stainless steel, nickel, titanium, tungsten, and thelike, connected, for example via cabling disposed within the elongatedproximal portion of the instrument, to a power supply, for example, anexternally disposed electrosurgical generator, and capable of generatingan electric field.

The present invention makes reference to a “floating electrode” or“floating element”. As used herein, the term “floating electrode” refersto one or more conductive elements formed from any suitable metallicmaterial, such as stainless steel, nickel, titanium, tungsten, and thelike, that, while disconnected from any power supply, is neverthelessbut capable of intensifying the electric field in proximity to theactive electrode and aid in bubble retention when the instrument is usedto vaporize tissue.

The present invention makes reference to a “filament”. As used herein,the term filament refers to one or more electrically powered conductiveelements resistively heated to high temperatures.

The present invention makes reference to a “return electrode”. As usedherein, the term “return electrode” refers to one or more poweredconductive elements formed from any suitable metallic material, such asstainless steel, nickel, titanium, tungsten, and the like, to whichcurrent flows after passing from the active electrode(s)and through theplasma field.

The term “proximal” refers to that end or portion which is situatedclosest to the user; in other words, the proximal end of anelectrosurgical instrument of the instant invention will typicallyinclude the handle portion.

The term “distal” refers to that end or portion situated farthest awayfrom the user; in other words, the distal end of an electrosurgicalinstrument of the instant invention will typically include the activeelectrode portion.

The present invention makes reference to the thermal treatment oftissue, more preferably soft tissue, even more preferably tumor tissue.As used herein, the term “tissue” refers to biological tissues,generally defined as a collection of interconnected cells that perform asimilar function within an organism. Four basic types of tissue arefound in the bodies of all animals, including the human body and lowermulticellular organisms such as insects, including epithelium,connective tissue, muscle tissue, and nervous tissue. These tissues makeup all the organs, structures and other body contents. The presentinvention is not limited in terms of the tissue to be treated but ratherhas broad application to the thermal treatment of any target tissue withparticular applicability to the ablation, removal and/or destruction ofbenign and cancerous tumors.

The instant invention has both human medical and veterinaryapplications. Accordingly, the terms “subject” and “patient” are usedinterchangeably herein to refer to the person or animal being treated orexamined. Exemplary animals include house pets, farm animals, and zooanimals. In a preferred embodiment, the subject is a mammal.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. In case of conflict, thepresent specification, including definitions, will control.

Utilities of the Present Invention

As noted above, the present invention is directed to high efficiencymonopolar or bipolar electrosurgical instruments and methods whichutilize radio frequency (RF) energy, electrically energized filaments,and/or non-coherent radiation emitted by heated filaments to destroytumors, form lesions, denaturize, desiccate, coagulate and ablate softtissues, as well as to drill, cut, resect and vaporize soft tissues,with or without externally supplied liquids, having particular utilityin the context of oncology, ear nose and throat (ENT), urology,gynecology, and laparoscopy, as well as general surgery.

Certain embodiments of the electrosurgical instrument of the presentinvention find particular utility in the treatment of tissue surfaces.Others are configured for sub-surface tissue treatment. Similarly, whilesome embodiments utilize the endogenous fluid of a “wet field”environment to transmit current to target sites, others require anexogenous irrigant. In certain embodiments, the irrigant is heated tothe boiling point, whereby thermal tissue treatment arises throughdirect contact with either the boiling liquid itself or steam associatedtherewith.

As described in further detail below, in one aspect, the presentinvention expands on the floating electrode concept. For example, thepresent invention relates to the design and deployment of novel“floating electrode” electrosurgical instruments that use steam/hotfluid to thermally treat target tissue, both at the surface and belowthe surface.

A further aspect of the present invention involves the construction anduse of hybrid monopolar/bipolar electrosurgical instruments that combinefeatures of monopolar and bipolar instruments to concentrate the energyin the desired region of the tissue to be treated. More particularly,the present invention relates to the discovery of a new type ofelectrosurgical device, a hybrid between monopolar and bipolarinstruments, that results in a novel electrosurgical therapeuticapproach for the thermal treatment of tissue. Unlike a bipolarinstrument, wherein the return electrode is mounted on the same shaft asthe active electrode, according to the principles of this invention, thereturn electrode is not mounted on the same shaft. Unlike monopolarinstruments, wherein the return electrode is mounted on the patient bodyfar away from the surgical site, according to the principles of thisinvention, the return electrode may be mounted on the patient body closeto the surgical site.

Such devices, according to the principles of the present invention,constitute hybrid instruments in the sense that the return electrodesize, shape and location is playing a critically important, andbeneficial role in distributing and focusing the RF current in thedesired area. For illustration purposes of this concept, consider a caseof treating a breast tumor. The return electrode may be externallyattached to the skin of the patient breast being treated, and theinstrument itself is inserted into the breast tissue/tumor, in closeproximity to the return electrode. When energized, the RF energy isconcentrated in the desired tissue/tumor region depending on the medicalneeds. More specifically, a specially designed return electrode (size,shape and position) and a specially designed active electrode(s) areused to optimize the energy distribution in the tissue over the desiredarea.

Usually the return (ground) electrode plays a “passive” role inelectrosurgery in the sense that it does not effect the electricalenergy distribution in the vicinity of the “active” electrode-the areawhere the tissue is being treated. This is a consequence of the returnelectrode being positioned too far away from the area being treated. Incontrast, if the main active electrode is in close proximity of thesurface of the body (skin), then positioning of a specially designedreturn electrode on the skin near area being treated can substantiallyand favorably effect the electrical energy distribution in the tissue.Moreover, the shape and position of return electrode can be changedduring procedure for the purpose of optimizing the clinical effects. Thedevices may be used in conjunction with various fluids, bodily fluids ordry fields. This unexpected discovery provides a new modality, or a newmethod of electrosurgical therapeutic approach for the thermal treatmentof tissue.

In a further aspect, the present invention relates to electrosurgicalinstruments that use hot filaments to generate plasma which may then beused to deliver energy for the thermal treatment of tissue. Moreparticularly, the present invention relates to the discovery of a newtype of plasma-based electrosurgical device that utilizes a hot filament(300-900° C.) to enhance plasma generation efficiency, ionization,arcing/sparking and effectiveness. In prior art plasma-basedelectrosurgical devices, like the argon beam coagulators mentionedabove, a sufficiently high electrical voltage must be applied to theelectrode, the voltage exceeding the breakdown threshold (electricalstrength) of the gaseous gap, at which point an electrical breakdown(ionization) takes place forming plasma channels between the electrodeand the tissue. The present invention utilizes a much more efficientapproach to achieve gas ionization (plasma formation). In particular,the present invention uses schemes to substantially and permanentlyreduce the electrical breakdown threshold of the gaseous media betweenthe electrode and the surface of the tissue. In this manner, the plasmacan be generated efficiently at lower voltages (0.5-3 kV) than otherwisepossible. According to the principles of this invention, this can beachieved, for example, by using a hot filament (electrode) tosubstantially reduce the electrical breakdown threshold of the gaseousgap between the electrode and the surface of the tissue. This resultarises from the substantial enhancement of the probability of electronemission from the heated filament. The filament also enhances theintensity of the RF field in its vicinity, making it easier to maintainthe plasma discharge. The heated filament also heats at least part ofthe discharge volume up to a high temperature and also seeds thedischarge channel with ionized particles making it easier to support thedischarge.

The instruments according to the principles of this invention mayoperate without gas flow, with a gas flow and with a reversed gas flow(gas suction). The instruments can operate in various fluids likeliquid, gas or air or a combination of all the above at variouspressures, including atmospheric pressure. The instruments according tothe principles of this invention may operate in electrically conductive,such as saline, or non conductive fluids. Various embodiments areillustrated, as examples, in FIGS. 42 to 60, the details of which arediscussed in further detail below. In all embodiments, a portion of thetissue surface can be coated with a thin layer of material with lowpotential of ionization. This material can be continuously evaporated toseed the discharge channel with neutral particles having low potentialof ionization, again lowering the threshold for generating andmaintaining the plasma channel. In this manner, the present inventionprovides a novel electrosurgical therapeutic approach for the thermaltreatment of tissue, an approach that may be used in conjunction withvarious irrigants, fluids, and bodily fluids or, alternatively, in a dryenvironment.

In yet a further aspect, the present invention relates to the deliveryof energy generated by an electrically heated filament to thermallytreat target tissue. More particularly, the present invention relates tothe discovery of a new type of minimally invasive instrument, based onminiature, intense sources of electromagnetic radiation in the form ofnon-coherent infra-red, visible and/or ultraviolet generated by anelectrically heated filament mounted inside a disposable instrument. Theinstruments based on the principles of this invention can treat eitherlarge or small tissue areas, depending on the designs.

Specifically, in order to create a lesion close to an outer or an innersurface of tissue, the tissue has to be heated. The heating takes placeif the tissue surface absorbs energy. The energy according to theprinciples of this invention is a non-coherent electromagnetic energy,such as infrared (IR), visible (V) and ultraviolet (UV) radiation,radiated by a filament heated to temperatures of approximately 500-2200°C. This radiation is absorbed by the surface of the tissue, heats thesurface and adjacent layer of the tissue creating layer of surfacelesion. The surface temperature rises as a function of time, tissueproperties, area of absorption, radiation power, and distance betweenthe filament and the tissue. By controlling the power of the source anddistance to the surface of tissue, one can control the temperature ofthe layer of the tissue as well as the thickness of the lesion layer.Illustrative embodiments of such a device, using the above principles,are described in further detail below. In all embodiments, the source ofradiation is an electrically heated open or encapsulated filament,heated to temperatures of approximately 500-2200° C., producingnon-coherent IR, visible and UV radiation of enough power. The mediabetween source and surface can be gaseous or liquid (conductive or nonconductive), bodily fluids, solid or combination of above. Gasventilation and liquid circulation, aspiration and irrigation may beused for cooling and/or removing byproducts and/or debris.

As an example, two embodiments are illustrated in FIGS. 61 & 62,discussed in greater detail below. The embodiment shown in FIG. 61includes an inflated transparent flexible bag with the heated filamentsource of non-coherent radiation inside, and also gasventilation/circulation for cooling. The embodiment shown in FIG. 62includes a directed movable energy source configured like a headlight(projector), with or without ventilation. However, many otherembodiments may utilize the same principles of this invention. Forexample: (a) elongated miniature linear versions (b), encapsulated ornon-encapsulated heated filament for insertion directly into tissue; (c)Filament/heater coated with an insulator; (d) an externalfilament/energy source coupled via a fiber optic to bring the energyinto the desired area to be treated; (e) same of the above with channelsin insulators for additional driving of RF current, monopolar and/orbipolar; (f) various geometries of the above instrument, likecylindrical, linear, spherical, curvilinear, polygonal and orcombinations of the above; (g) embodiments can include a flexible bagwith controlled transparency and gas ventilation for cooling; (h)miniature versions and combinations of the above. Thus, the presentinvention provides a new therapeutic approach for thermal tissuetreatment, a method that may be used in conjunction with various fluids,bodily fluids or dry fields.

The tissue treatment instruments of the present invention may be used inconjunction with existing diagnostic and imaging technologies, forexample imaging systems including, but not limited to, MRI, CT, PET,x-ray, fluoroscopic, and ultrasound. Such imaging technology may be usedto monitor the introduction and operation of the instruments of thepresent invention. For example, existing imaging systems may be used todetermine location of target tissue, to confirm accuracy of instrumentpositioning, to assess the degree of thermal tissue treatment (e.g.,sufficiency of tissue removal), to determine if subsequent proceduresare required, and to assist in the atraumatic removal of the instrument.

As noted above, the instruments of the present invention find utility inthermal tissue treatment, more particularly in thermal treatment oftumor tissue, both benign and cancerous, to destroy tumors, formlesions, denaturize, desiccate, coagulate and/or ablate tumor tissues,as well as to drill, cut, resect and vaporize tumor tissues, with orwithout externally supplied liquids. Though the present invention is notparticularly limited to the treatment of any one specific disease or theremoval of any one specific type of tumor, the instruments of thepresent invention nevertheless find particular utility in the treatmentand removal of liver, breast, bladder and spinal tumors, uterinefibroids, ovarian cysts, and colon polyps as well as the treatment ofnoncancerous conditions such as endometriosis.

Illustrative Embodiments of the Present Invention

Hereinafter, the present invention is described in more detail byreference to the exemplary embodiments. However, the following examplesonly illustrate aspects of the invention and in no way are intended tolimit the scope of the present invention. As such, embodiments similaror equivalent to those described herein can be used in the practice ortesting of the present invention.

Referring to FIGS. 1 through 6, which depict an insulator of anelectrosurgical instrument of the present invention that is particularlysuited to thermally treating patient tissue, insulator 20 has a distalend portion 22, a proximal end portion 24 and mid-portions 26. Distalend portion 22 has formed in its proximal face cylindrical recesses 28.Proximal end portion 24 has axial cylindrical openings 30 axiallyaligned with recesses 28. Mid-portions 26 have formed in lower surface32 channels 34. Insulator 20 is made from a suitable dielectricmaterial, examples of which include, but are not limited to, alumina,zirconia, and high-temperature polymers.

Referring to FIGS. 7 through 10, which depict an active electrode of anelectrosurgical instrument of the present invention that is particularlysuited to thermally treating patient tissue, active electrode 40 has adistal portion forming parallel cylindrical portions 42 connected byflange 44 to proximal conductor 46. Electrode 40 may be formed from anysuitable metallic material, examples of which include, but are notlimited to, stainless steel, nickel, titanium, tungsten, and the like.

FIGS. 11 through 15 depict a floating electrode for an electrosurgicalinstrument of the present invention that is particularly suited tothermally treating patient tissue. As shown herein, the floatingelectrode 50 forms adjacent channels having a common flange 52, andlateral flanges 54 and wall 56. Flanges 52 and 54 have ends 58 formed toa radius. However, the present invention is not limited to the depicteddesign and includes alternate floating electrode embodiments, such asthose described in co-pending U.S. patent application Ser. No.10/911,309 (published as US 2005-0065510) and Ser. No. 11/136,514(published as US 2005-023446) cited above, the contents of which areincorporated by reference herein in their entirety. Referring now toFIGS. 16 to 21, which depict a distal portion of an electrosurgicalinstrument of the present invention formed from the components of FIGS.1 through 15, the distal portion of probe 60 is an assembly in whichdistal portions 42 of active electrode 40 are positioned within channelportions 34 of insulator 30. Floating electrode 50 is positioned betweendistal portion 22 and proximal portion 24 of insulator 20. Dielectriccoating 62 covers flange 44 and conductor 46 of active electrode 40.Conductor 40 is connected by means within the probe 60 and electricalcable to a suitable electrosurgical generator.

FIG. 22 depicts probe 60 in use, fully or partially submerged inirrigant (either endogenous to site or exogenously supplied). Flanges 52and 54 of floating electrode 50 contact the tissue. Distal portions 42of active electrode 40 may contact the tissue, or may contact the fluidin a gap between the electrode 40 and the tissue. Fluid surrounding thedistal end of probe 60 is conductive. It may be supplied to the site asa conductive liquid such as standard saline, or may be supplied to thesite as a non-conductive irrigant such as water, the fluid becomingconductive by contamination by body fluids such as blood, or by ablationby-products.

During use, current (indicated by arrows) flows from active electrode 40to a return electrode (not shown), either at a remote site or mounted onthe instrument 60. Current flows from distal portions 42 of activeelectrode 40 through tissue in contact with or in close proximity toportions 42. Some current flows through the tissue to the returnelectrode. A portion of the current flows through the tissue to radiusedportions 58 of flanges 52 and 54 of floating electrode 50 in contactwith the tissue to portions of floating electrode 50 in lower potentialportions of the electric field. This current then flows from floatingelectrode 50 to conductive fluid in contact therewith, and then throughthe fluid to the return electrode. The efficiency of probe 60 forthermally treating tissue is enhanced by the elimination of regions ofhigh current density. Such regions of high current density cause boilingof irrigant in close proximity, and arcing through the steam bubblesformed so as to vaporize tissue. The absence of these regions allows thedevice to be used at higher power levels for more rapid tissue treatmentwithout creating these undesirable vaporizing sparks. Specifically,portions of flanges 52 and 54 which contact tissue are radiused so as toeliminate sharp corners which create regions of high current density. Inaddition, portions 42 of active electrode 40 are also rounded toeliminate sharp edges which create regions of high current density.

FIGS. 23 through 27 depict the distal portion of another thermaltreatment electrosurgical instrument of the present invention. Probe 70has a planar active electrode 72 suspended by distal dielectric endpiece 74 and proximal dielectric end piece 76 in an inverted channelformed by floating electrode 78. Lateral edges 80 of active electrode72, and edges 82 of floating electrode 78 are radiused. Lower surface 86of active electrode 72 is recessed distance 88 from the plane of edges82 of floating electrode 78. Conductor means 90 within probe 70 andcabling connect active electrode 72 to a suitable electrosurgicalgenerator. Tubular member 92 is connected by means within probe 70 to anexternal conductive irrigant source.

Although the active electrode assembly is depicted as a having asquare/rectangular profile and/or cross-section, the invention is notlimited to the depicted configuration. So long as a particularconfiguration provides the requisite confined space, more particularlythe presence of a fluid-fillable cavity defined between the active andfloating electrodes, other geometries may be contemplated including, butnot limited to, electrode assemblies having rounded, circular,elliptical, and polygonal profiles.

Referring now to FIG. 28, which depicts probe 70 in use in a “dryfield”, conductive irrigant 96 may be supplied by tubular member 92 tothe interior of the distal portion of probe 70, between the uppersurface of active electrode 72 and the interior surface of floatingelectrode 78. Current (indicated by arrows) flows from active electrode72 to a return electrode, either remotely located or on probe 70. Aportion of the current flows through conductive liquid surroundingactive electrode 72 to floating electrode 78 and therethrough to tissuein contact with or close proximity to edges 82. Current flowing from thefloating electrode 78 to the tissue in this manner is conducted throughdirect contact or through conductive fluid in close proximity. A secondportion of the current flows from the active electrode 72 to the tissuethrough conductive fluid between active electrode 72 and the tissue.Current flowing through conductive irrigant 96 heats irrigant 96primarily in the regions in which active electrode 72 and floatingelectrode 78 are in close proximity. If the current flow is sufficientlyhigh related to the flow rate of conductive irrigant 96, boiling ofirrigant 96 occurs. Expanding steam and irrigant flow from tubularmember 92 causes heated liquid and steam to flow into the region betweenactive electrode 72 and the tissue. Thermal treatment of the tissue isaccomplished through contact with heated liquid and steam, and throughflow of current. The relative proportion of the two depends on the powersupplied and the flow rate of conductive irrigant 96.

FIG. 29 depicts probe 70 in use in a conductive liquid environment.Conductive irrigant 96 is supplied by tubular member 92 to the interiorof the distal portion of probe 70, between the upper surface of activeelectrode 72 and the interior surface of floating electrode 78. Currentflows from active electrode 72 to a return electrode, either remotelylocated or on probe 70. A portion of the current flows throughconductive liquid surrounding active electrode 72 to floating electrode78 and therethrough to conductive liquid in contact with the exteriorsurfaces of floating electrode 78. A second portion of the current flowsfrom the active electrode 72 to the tissue through conductive fluidbetween active electrode 72 and the tissue. Current flowing throughconductive irrigant 96 heats irrigant 96 primarily in the regions inwhich active electrode 72 and floating electrode 78 are in closeproximity. If the current flow is sufficiently high related to the flowrate of conductive irrigant 96, boiling of irrigant 96 occurs. Expandingsteam and irrigant flow from tubular member 92 causes heated liquid andsteam to flow into the region between active electrode 72 and the targettissue. Thermal treatment of the tissue is accomplished through contactwith heated liquid and steam, and through flow of current. The relativeproportion of the two depends on the power supplied and the flow rate ofconductive irrigant 96. As with the instrument 60 previously hereindescribed, probe 70 is designed to minimize or eliminate regions of highcurrent density which cause arcing and tissue vaporization.Particularly, edges 82 of floating electrode 78 which contact targettissue are rounded to eliminate regions of high current density andarcing which may result therefrom. Also, lateral edges 80 of activeelectrode 72 are radiused to prevent arcing between active electrode 72and the tissue or between electrode 72 and floating electrode 78. Lowersurface 86 of active electrode 72 does not have features such asgrooves, protuberances, recesses which increase current density, but issmooth. These features, individually and/or in combination, allow probe70 to be used at higher power levels for more rapid tissue treatmentwithout arcing and the resulting undesirable tissue vaporization.

FIGS. 30 through 32 depict the distal portion of an electrosurgicalinstrument of the present invention that is particularly suited to thethermal treatment of tissue, more particularly sub-surface tissuetreatment. While the previous embodiments are designed for surfacetreatment, electrosurgical instrument 100 thermally treats tissue intowhich it is inserted. Probe 100 is formed from a dielectric tube 102having a sharpened, tapered or conical distal end 104 that facilitatesatraumatic insertion into the target tissue. To distal end 104 ismounted active electrode 106 connected by conductor 108 insulated bydielectric coating 109 and means within probe 100 and cabling to asuitable electrosurgical generator. Tubular conductive member 110 isassembled to dielectric tube 102 near its distal end, and connected byconductor 112 insulated with dielectric coating 114 to a control elementin the handle portion of probe 100. The control element has a firstposition in which conductor 112 is not connected to the electrosurgicalgenerator, and a second position in which the conductor 112 is connectedto the generator output such that when the generator is activated RFvoltage is applied to member 110.

During use, probe 100, while energized, is first inserted into thetissue, tubular member 110 functioning as a floating electrode, theswitching means being in its first position. When probe 100 is insertedto the desired depth, switching means is put in its second position andRF energy is supplied to conductive member 110 so as to treat tissue inclose proximity.

FIGS. 33 through 35 depict another embodiment of an electrosurgicalinstrument of the present invention that is particularly suited tothermal treatment of tissue into which it is inserted. Probe 120, thedistal portion of which is shown has a first conductive tubular member122 having a distal end 124 in which is mounted dielectric member 126.Member 122 has a plurality of ports or perforations 128. Second tubularmember 130 is coaxially positioned within member 122, and has a distalend 132 positioned within a recess in dielectric member 126. Secondtubular member 130 with lumen 133 has a plurality of perforations 134.Proximal end 136 of member 122 is mounted to tubular member 138, thedistal end of first tubular member 138 and proximal portion of member122 are covered by dielectric coating 140. Second tubular member 130 isconnected by means within probe 120 and cabling to a suitableelectrosurgical generator. Region 142 is defined by the interior surfaceof first tubular member 122 and the exterior surface of second tubularmember 130. Second tubular member 130 is connected by means within probe120 and tubing to an external source for conductive irrigant.

Referring now to FIG. 36 depicting a portion of probe 120 during use,probe 120 is inserted into tissue to be thermally treated. Conductiveirrigant 150 is supplied to lumen 133 of second tubular member 130.Lumen 133, perforations 134, region 142, and perforations 128 togetherform a flow path for irrigant 150 from lumen 133 of second tubularmember 130 to region 144 between the external surface of probe 120 andthe tissue into which it is inserted. Current flows from second tubularmember 132 which acts as an active electrode, through conductiveirrigant 150 to first tubular member 122, and therethrough to adjacenttissue via conductive irrigant in the gap between probe 120 and thetissue, and finally to a return electrode (not shown), either remotelylocated or on probe 120. First tubular member 122 is not connected tothe electrosurgical unit, but has a floating potential between that ofthe active electrode (second tubular member 130) and the tissue. Currentflowing through irrigant 150 in region 142 heats the irrigant causing itto boil. Irrigant 150 flowing from region 142 through perforations 128is a two-phase mixture of steam and liquid which heats tissue with whichit is in contact. The relative portions of steam and liquid aredetermined by the flow rate of irrigant 150, and by the applied powerlevel. Decreasing the power or increasing the flow rate will cause theliquid phase to increase. Tissue thermally treated by probe 120 isheated by the irrigant and by resistive heating caused by current flow.The RF energy supplied to probe 120 has characteristics selected tominimize arcing within bubbles in the irrigant, and between member 122and adjacent tissue.

FIG. 37 is an illustrative example of the above-described hybridelectrosurgical instrument of the present invention. In particular, theinstrument of FIG. 37 includes an active electrode 400 which is embeddedin the tumor 406 and a return electrode 402 on the instrument whichcontacts a free surface of the tissue near the tumor so as toconcentrate the current flow 404 between the active and returnelectrodes, through the tumor.

An alternate embodiment of the above-described hybrid electrosurgicalinstrument of the present invention is depicted in FIG. 38. Theinstrument of FIG. 38 includes an active electrode 410 which is embeddedin the tumor 416 and a return electrode 412 not on the instrument whichcontacts a free surface of the tissue near the tumor so as toconcentrate the current flow 414 between the active 410 and returnelectrodes 412, through the tumor.

FIGS. 39 through 41 depict the distal portion 500 of an alternateembodiment designed to be embedded in a tumor 512 to go undergotreatment, the probe having a tubular active electrode 502 covered bydielectric coating 508 except for uninsulated portion 510 withperforations 504 such that irrigant 506 supplied to the active electrodeflows from the electrode through perforations 504 so as to preventdesiccation and burning of tissue in contact with the electrode. In analternate embodiment also designed to be embedded in a tumor to goundergo treatment, the probe distal portion construction is identical tothat of distal portion 500, with the exception that uninsulated portion510 of active electrode 502 is formed from a porous metallic materialand perforations 504 are eliminated. Irrigant supplied to the activeelectrode flows from the electrode 502 through the porous material so asto prevent desiccation and burning of tissue in contact with theelectrode. In yet another embodiment, perforations 504 are eliminated,and irrigant is supplied to the site by an annular passage betweenactive electrode 502 and dielectric coating 508. As with the previousembodiments, irrigant so supplied prevents desiccation and burning oftissue in contact with the electrode.

Most widely used electro surgical electrodes-ablators, coagulators,evaporators, cutters, electrodes for lesion forming and electrodes fortreatment of tumors (often referred to as tumor ablation) need to bevery close to or in direct contact with the tissue being treated inorder to be effective. Electrosurgical instruments like the Argon BeamCoagulator (Conmed Corporation, Utica, N.Y.) and other similar devicesoperate without direct contact with the tissue. These instruments employa gaseous gap between the instrument's electrode and the tissue. Theelectrode is insulated, and high voltage is applied to the gaseous gapbetween electrode and the surface of the tissue. If sufficiently highvoltage is applied to the electrode, the electric field exceeds thebreakdown threshold (electrical strength) of the gaseous gap, andelectrical breakdown takes place forming a plasma channel between theelectrode and the tissue. This electrically conductive plasma channelacts as a non-contact extension of the electrode, allowing treatment ata “stand-off' distance. Instruments based on this scheme, sometimesreferred to as plasma torches, generally require very high voltages (upto 10-20 kV), which are beyond the capability of standard, generalpurpose, commonly available electrosurgical radio-frequency (RF)generators. In addition, plasma torches require specially shapedelectrodes, a flow of gas (usually a noble gas jet), a speciallydesigned nozzle to control the gas flow, and high voltage circuitry tobring high voltage to the proximity of the surgical field.

Advanced, non-contact, plasma-based electrosurgical instrumentsconstructed in accordance with the principles of this invention may beoperated in the plasma torch regime yet are compatible with “standard”electrosurgical RF generators. The electrosurgical instruments of thepresent invention (which may be single-use disposables) can operatewithout a gas flow, with a gas flow and with a reversed gas flow (gassuction). The electrosurgical instruments of the present inventionsubstantially and permanently reduce the electrical breakdown thresholdof the gaseous gap between the electrode and the surface of the tissue.In addition, the plasma can be generated efficiently at low voltages(0.5-2 kV), thereby allowing for the use of general purpose, standardelectrosurgical RF generators. Among the factors employed to achievethis goal are increasing the probability of electron emission fromelectrode; heating at least part of the discharge volume; seeding thedischarge channel with ionized particles; filling the discharge channelwith gas having a low rate of attraction of electrons; and seeding thedischarge channel with neutral particles with low potential ofionization.

Referring now to FIGS. 42 through 44 which depict an embodiment of anelectrosurgical instrument of the present invention that utilizes a hotfilament to generate plasma channel particularly suited to the thermaltreatment of surfaces, probe 200 has a proximal portion 202 forming ahandle having a proximal end 204 from which passes electrical cable 206which is connected to a suitable electrosurgical generator, and a distalend 208 from which protrudes elongated instrument distal portion 210.Portion 210 has a proximal end 212 mounted to handle portion 202, and adistal end 220. Activation button 216 controls the electrosurgicalgenerator to which probe 200 is connected by cable 206. Handle portion202 contains batteries 218.

Referring now to FIGS. 45 through 49 depicting the active distal end of220 of distal portion 210 of probe 200, elongated tubular member 222with lumen 223 has mounted to its distal end closed-end tubular member224 to which is mounted insulator 226. Insulator 226 has a first recess228 formed coaxial with insulator 226, recess 228 having a planarsurface 230. Surface 230 has formed therein second recess 232. Insulator226 has formed therein passages 234 between second recess 232 andsurface 234 of insulator 226. Filament wire 236 is connected by tubularmembers 238 to wires 240 in lumen 223 of tubular member 222, wires 240being connected by circuitry within handle portion 202 to batteries 218,and by cable 206 to the electrosurgical generator such that depressingactivation button 216 causes batteries 218 to supply the battery voltageto filament 236, and the electrosurgical generator to supply RF voltageto filament 236. Insulation 242 covers wires 240. Insulation 244 coversthe proximal portion of tubular members 238, and the distal portion ofwires 240.

FIG. 50 depicts probe 200 in use thermally treating a tissue surface.Direct current power supplied by batteries 218 heats filament wire 236which also heats air and other gasses in proximity to filament wire 236.RF power from the electrosurgical generator is also applied to filamentwire 236. The high temperature of filament 236 increases the ease withwhich electrons may be ejected from filament 236. Heating of the air andother gases in proximity to filament 236 decreases the resistance of theair and gases to electrical breakdown. These two effects together allowthe formation of plasma channels through the air and gases in the gapbetween filament wire 236 and tissue in close proximity. Powertransmitted through these channels interacts with the surface of thetissue thermally treating the tissue and desiccating tissue near thesurface. Movement 250 of probe 200 relative to the tissue creates alinear region of treatment, depth 252 of the thermal effect beingdetermined by the applied power and the rate of movement 250.

Referring now to FIGS. 51(A) and 51(B) depicting schematicrepresentations of probe 200 of FIG. 42 in use, electrosurgicalgenerator 260 is connected by wire 262 to return electrode pad 264, andby wire 265 to first wire 241 of wires 240 connected to batteries 218and filament 236 in distal end assembly 220. Heating of filament 236 bypower from batteries 218 and RF power from generator 260 togetherproduce arcs 266 between filament 236 and tissue in close proximity.Desiccation by heat from arcs 266 creates local layer 268 of dryinsulating tissue. Secondary arcing 270 may occur beneath layer 268.Current 272 flows from the region near arcs 266 through the tissue toreturn electrode 264.

FIG. 52(A) schematically depicts distal end assembly 220 of probe 200.Batteries 218 via wires 240 and conductive members 238 to filament 236.Wire 265 conducts power from the RF generator to first wire 241 andtherefrom via conductive member 238 to filament 236. Power frombatteries 218 heats the filament. Power from the RF generator causesarcing 266 and produces the desired clinical effect. FIGS. 52(B) and (C)show that insulator 226 may have a variety of cross-sections. However,those shown are merely illustrative and not intended to limit the scopeof the invention.

FIG. 53 depicts an alternate embodiment of distal end assembly 220 ofprobe 200. Filament 236 has a coil for enhanced heating of the regionsurrounding filament 236 for increased probe efficiency.

FIG. 54 depicts an alternate embodiment of distal end assembly 220 ofprobe 200 in which filament 236 is integral with conductive members 238,the filament portion being of a reduced cross-section.

FIG. 55 depicts an alternate embodiment of distal end assembly 220 ofprobe 200 in which the filament has been deleted. Conductive members 238have distal ends which are in sufficiently close proximity to producemicro-arcing 276 therebetween when voltage from power supply 218 isapplied.

FIG. 56 depicts an alternate embodiment of distal end assembly 220 ofprobe 200 in which heating at the distal region of the probe isaccomplished by a UV lamp 278 connected to power supply 276, rather thanby a filament.

FIG. 57 depicts an alternate embodiment of distal end assembly 220 ofprobe 200 in which the conductive member 238 has a sharpened distal endhaving a low included angle so that the distal portion is heated to anelevated temperature by arcs 266. Heating of the distal portion isenhanced by insulator 226 which closely conforms to member 238 so as toprevent radiant or convective heat loss from member 238.

FIG. 58 depicts an alternate embodiment of distal end assembly 220 ofprobe 200 in which conductive member 238 has a sharpened distal endwhich is in contact with a portion of insulator 226 such that dielectricbreakdown produces micro-sparking which heats the region causing arcs266 to occur.

FIG. 59 depicts an alternate embodiment of distal end assembly 220 ofprobe 200 in which conductive member 280, connected via resistor 282 towire 262 of the return electrode circuit, is positioned in closeproximity to member 238 such that micro-arcing occurs between members280 and 238, the micro-arcing producing sufficient heat to allow arcing266. Resistor 282 limits current through member 280.

As noted above, the embodiment depicted in FIG. 60 corresponds to a newtype of minimally invasive instrument, based on miniature, intensesources of infra-red, visible and ultra violet generated by anelectrically heated filament mounted inside a disposable instrument.More particularly, FIG. 60 depicts an alternate embodiment of distal endassembly 220 of probe 200 configured for gas flow through the distalportion of probe 200. In FIG. 60(A) gas 292 supplied to nozzle 290floods the area around filament 236 and arcs 266. In FIG. 60(B) air andgases 294 surrounding arcs 266 and filament 236 are evacuated throughnozzle 290.

As noted above, FIG. 61 depicts an alternate embodiment 600 for treatinga surface in a body cavity in which a source of electromagnetic energy,which, in this case is a miniature high-intensity infrared lamp 602 ispositioned within a transparent inflatable bag 606. The assembly ispositioned within a body cavity to be thermally treated. Gas 604 isinjected into the bag causing it to inflate and conform to the tissuesurface. The IR lamp 602 is energized causing heating of the tissue incontact with the bag 604. Gas flow into and out of the bag is maintainedduring treatment.

FIG. 62 depicts an alternate embodiment for treating a surface using aprobe having at its distal tip 700 a miniature infrared lamp 702, a lens704 and a reflector 706 for directing heat 708 from the lamp to thetissue surface. The profiles of reflector 706 and lens 704 togetherdetermine the energy distribution. In a preferred embodiment theprofiles of reflector 706 and lens 704 together produce a uniformdistribution across the distal opening of tip 700. In other embodiments,the profiles can cooperate to form distributions such as a concentratedspot, line, annulus, or other predetermined desired profile.

INDUSTRIAL APPLICABILITY

The minimally invasive monopolar and bipolar electrosurgical instrumentsof the present invention find utility in the area of remote tissueablation and lesion formation, to destroy tumors, form lesions,denaturize, desiccate, coagulate and ablate soft tissues, as well as todrill, cut, resect and vaporize soft tissues, with or without externallysupplied conductive or non-conductive liquids (i.e., in the context ofboth wet and dry field electrosurgery). More particularly, theelectrosurgical instruments of the present invention are designed toheat tissue from the outside in, to provide homogeneous energydeposition using less power, which in turn yields a highly homogeneouslesion.

In this manner, the electrosurgical instruments of the present inventionallow one to effectively and efficiently control of the shape and sizeof the lesion formed, to thereby avoid unnecessary complications andundesired side effects. Such instruments are particularly useful in thecontext of oncological, ENT, urological, gynecological, and laparascopicprocedures, as well as in the context of general surgery.

All patents and publications mentioned herein are incorporated byreference in their entirety. Nothing herein is to be construed as anadmission that the invention is not entitled to antedate such disclosureby virtue of prior invention.

While the invention has been described in detail and with reference tospecific embodiments thereof, it is to be understood that the foregoingdescription is exemplary and explanatory in nature and is intended toillustrate the invention and its preferred embodiments. Through routineexperimentation, one skilled in the art will readily recognize thatvarious changes and modifications can be made therein without departingfrom the spirit and scope of the invention.

Other advantages and features will become apparent from the claims filedhereafter, with the scope of such claims to be determined by theirreasonable equivalents, as would be understood by those skilled in theart. Thus, the invention is intended to be defined not by the abovedescription, but by the following claims and their equivalents.

What is claimed:
 1. An electrosurgical instrument for thermal tissuetreatment comprising: a. an elongate shaft having a proximal end, adistal end and a longitudinal axis, wherein said proximal end isconfigured for connection to a power source and said a distal end isconfigured for connection to an electrode assembly; b. an electrodeassembly mounted to the distal end of said elongate shaft, saidelectrode assembly comprising: i. an active electrode formed from anelectrically conductive material and connected via one or moreconnecting elements disposed within said shaft to a power source; ii. afloating electrode formed from an electrically conductive material thatis positioned in close proximity said active electrode and not directlyelectrically connected to either the linear elongate shaft or a powersource; and iii. an insulator formed from a nonconductive dielectricmaterial that separates said active and floating electrodes to define acavity therebetween; and c. a means for supplying an irrigant to saidcavity; wherein powering of said active electrode in the presence of anirrigant results in flow of current from said active electrode to saidfloating electrode, heating of said irrigant and generation of steam insaid cavity, wherein heated irrigant and steam flow out of said cavityand thermally treat target tissue upon contact.
 2. The electrosurgicalinstrument of claim 1, wherein said tissue comprises tumor tissue. 3.The electrosurgical instrument of claim 2, wherein said thermaltreatment results in tumor destruction, lesion formation, or thedenaturization, dessication, coagulation or ablation of tumor tissue. 4.The electrosurgical instrument of claim 1, further comprising a returnelectrode.
 5. The electrosurgical instrument of claim 1, wherein saidactive electrode and said floating electrode comprise concentric tubesand said cavity defined between said active and floating electrodescomprises an annular cavity, further wherein said active electrodecomprises a single-lumened tube having a first set of perforations fordelivering said irrigant to said annular cavity and said floatingelectrode comprises a single-lumened tube having a second set ofperforation for delivering said heated irrigant to said target tissue.6. The electrosurgical instrument of claim 5, wherein said first andsecond set of perforations are offset.
 7. The electrosurgical instrumentof claim 1, wherein said insulator comprises a conical tip disposed atthe distal end of said electrode assembly, said conical tip beingsufficiently sharp to permit insertion of said electrode assembly intosaid target tissue.